We have a stake in all the past life of the globe. It is no doubt a scientific fact that your existence and mine were involved in the first cell that appeared, that the first zoophyte furthered our fortunes, that the first worm gave us a lift. Great good luck came to us when the first pair of eyes were invented, probably by the trilobite back in Silurian times; when the first ear appeared, probably in Carboniferous times; when the first pair of lungs grew out of a fish's air-bladder, probably in Triassic times; when the first four-chambered heart was developed and double circulation established, probably with the first warm-blooded animal in Mesozoic times. These humble forms started the brain, the nervous system, the circulation, sight, hearing, smell; they invented the liver, the kidneys, the lungs, the heart, the stomach, and led the way to every organ and power my body and mind have to-day. They were the pioneers, they were the dim remote forebears, they conserved and augmented the fund of life and passed it along. All their struggles, their discipline, their battles, their failures, their successes, were for you and me. Man has had the experience of all the animals below him. He has suffered and struggled as a fish, he has groveled and devoured as a reptile, he has fought and triumphed as a quadruped, he has lived in trees as a monkey, he has inhabited caves with the wolf and the bear, he has roamed the forests and plains as a savage, he has survived without fire or clothes or weapons or tools, he has lived with the mastodon and all the saurian monsters, he has held his own against great odds, he has survived the long battles of the land and the sea, he weathered the ice-sheet that overrode both hemispheres, he has seen many forms become extinct. In the historic period he has survived plague and pestilence, and want and famine. What must he have survived in prehistoric times! What must he have had to contend with as a cave-dweller, as a tree-dweller, as a river-drift man! Before he had tools or weapons what must he have had to contend with! Nature was full of sap and rioted in rude strength well up to Quaternary times, producing extravagant forms which apparently she had no use for, as she has discontinued them. In all these things you and I had our part and lot; of this prodigal outpouring of life we have reaped the benefit; amid these bizarre forms and this carnival of lust and power, the manward impulse was nourished and forwarded. In Eocene times nearly half the mammals lived on other animals; it must have been an age of great slaughter. It favored the development of fleetness and cunning, in which we too have an interest. Our rude progenitor was surely there in some form, and escaped the slaughter. Then or later it is thought he took to the trees to escape his enemies, as the rats in Jamaica have taken to the trees to escape the mongoose. To his tree-climbing we probably owe our hand, with its opposing thumb.